MBMS is one technology by which a shared network resource transmits data from one data resource to multiple targets. In order to effectively utilize the mobile network resource, 3GPP (3rd Generation Partnership Project) proposes MBMS service in R6, that is, the mobile network is provided with the point-to-multipoint service in which data is transmitted from one data resource to multiple users, so as to achieve the sharing of the network resource, and in turn improve the network resource, particularly the utilization efficiency of the valuable air interface resource. MBMS can not only realize the low-speed message-class multicast and broadcast of pure text, but also achieve the multicast and broadcast of high-speed multimedia service, providing various abundant video, audio and multimedia services whereby the development of mobile communication has better perspective.
The setup model of the MBMS service system is shown in FIG. 1.
BM-SC (broadcast and multicast service center) is a new mobile network function utility which is the entrance of the content provider, used for the authorization and the initiation of MBMS bearing service in the mobile network and for transmitting the MBMS content according to schedule.
For the existing WCDMA packet network function utilities, i.e., GGSN (General Packet Radio Service Gateway Support Node), SGSN (Serving General Packet Radio Service Support Node), RAN (Radio Access Net) and UE (User Equipment), it is also needed to add functions and processes associated with MBMS.
RAN includes RNC and Node B. MBMS introduces into RAN three new logical channels, which are MCCH (MBMS point-to-multipoint Control Channel), MTCH (MBMS point-to-multipoint Traffic Channel) and MSCH (MBMS point-to-multipoint Scheduling Channel). The three newly added logical channels are all mapped onto FACH (Forward Access Channel) which is mapped onto SCCPCH (Secondary Common Control Physical Channel). MBMS also introduces one new physical channel, MICH (MBMS point-to-multipoint indicator) into RAN. What is carried on MICH is MBMS notification indicator with small amount of information and will be read in by UE (User Equipment) in a very short period of time. While what is carried on MCCH is detailed MBMS service notification, RB (Radio Bearer) configuration and other MBMS control information, when the amount of MBMS services carried by a cell is relatively large, the amount of information carried by MCCH is very large and will be read in by UE in a relatively long period of time. Hence, UE can determine whether it is necessary to read in MCCH message through monitoring MICH, so as to achieve the discontinuous reception of MCCH and prolonged stand-by time of UE.
MBMS service has two transmitting manners in RAN, i.e., PTP (point to point) and PTM (point to multipoint). With PTP transmitting manner, the data is transmitted through DTCH (Dedicated Traffic Channel) which is uniquely occupied by one UE, while with PTM manner the data is transmitted through MTCH (common logical channel) which is shared by multiple UEs.
For supporting MBMS service, RAN has to have MBMS supporting ability, represented by the MBMS supporting ability of a cell, that is, MBMS service only can be transmitted in the cell which supports MBMS. If the cell supports MBMS, during the setting up of the common channels in the cell, RNC needs to notify Node B to set up MICH physical channel in the cell and the setup of MICH channel must be bound with the setup process of FACH and SCCPCH bearing MCCH logical channel. The detailed process is shown in FIG. 2. In FIG. 2, to request the setup of MCCH-carrying FACH and SCCPCH, RNC transmits to the Node B the COMMON TRANSPORT CHANNEL SETUP REQUEST which also carries configuration parameters required by the setup of MICH physical channel therewith. If the cell supports MBMS, Node B sets up MCCH-carrying FACH and SCCPCH after receiving the message, and sets up and activates the MICH physical channel according to the MICH parameters carried in the message. At the same time, the association relationship between MICH and SCCPCH bearing the MCCH is built up. Then a message of COMMON TRANSPORT CHANNEL SETUP RESONSE is returned to RNC which, upon receiving the response message, broadcasts in the broadcast message the information of MCCH-carrying SCCPCH and FACH to all UEs in the cell. At this point, MCCH and MICH are successfully set up and the cell can support MBMS service. If the cell does not support MBMS, Node B does not set up MICH channel and FACH and SCCPCH used for bearing MCCH after receiving the message and returns the message of COMMON TRANSPORT CHANNEL SETUP FILURE to RNC with the indicated reason of failure, “MICH not supported”. At this point, the setup of MCCH and MICH is failed and the cell can not support MBMS service.
According to the current 3GPP protocol, Node B does not report the MBMS support ability of the cell to RNC, therefore RNC does not know whether the cell of Node B supports MBMS or not. Before setting up the MICH channel and the FACH and SCCPCH bearing the MCCH, RND does not know whether the setup can be successful in the corresponding cell. RNC does not know that the cell does not support MBMS until RNC attempts the setup with the Node B returning “failure” and the indicator being “MICH not supported”. Therefore, according to the current protocol, RNC can not obtain the MBMS ability information of the cell before attempting the setup of MICH channel. Normally, RNC can learn the MBMS supporting ability of the cell only by making the configuration and the like and then it notifies the Node B to set up MICH channel and MCCH channel in the corresponding cell. However, the method, similar to the configuration method, is often unreliable, furthermore, the complication degree of the system maintenance is greatly increased.